They said the committee would be headed by a Lebanese army general and consist of representatives from the Saudi-backed government of Yemen’s President Abd-Rabbu Mansour Hadi and from the rival Houthi movement, which is allied to Iran.

Both sides arrived at a hotel in the Swiss city of Biel on Saturday to attend a fifth day of talks aimed at halting the eight-month conflict in the Arab world’s poorest nation, which has killed thousands of people and caused widespread destruction and a major humanitarian crisis.

A supposed one-week truce came under strain on Friday when troops loyal to Hadi seized an important northwestern city and a military base from Houthis who still control the capital Sanaa, residents and tribal sources said.

Planes and gunboats from a Saudi-led military coalition also bombarded targets in northern Yemen, residents said.

The United Nations Special Envoy for Yemen voiced deep concern at “numerous reports of violations of the cessation of hostilities”, a U.N. statement said on Friday.

Yemen, which was swept by mass Arab Spring-inspired protests in 2011, was this year plunged into war after the Houthis overthrew the Sanaa government, prompting Saudi Arabia and other Arab states in March to launch a wide-scale bombing campaign.

The U.N. talks started away from television cameras on Tuesday and have been marked by distrust, with each side accusing the other of violating the truce.

Face-to-face talks between Hadi’s government and the Houthi group have not occurred since Wednesday evening, after the Houthis rejected demands for the release of detained senior officials, including Yemen’s defense minister and Hadi’s brother, said sources close to the talks.

The U.N. special envoy, Ismail Ould Cheikh Ahmed, is shuttling between the two sides to try and bridge differences.

The Houthis say they are ready to free the prisoners once a permanent ceasefire is agreed, another source close to the talks told Reuters.

Hospital sources said on Saturday that limited medical aid had reached a few Houthi-controlled districts in the central city of Taiz, one of the worst-affected cities.